[Openmp-dev] Phoronix numbers for clang-omp compiler

[Jack Howarth]

Alexey,
      This wouldn't be the first time that Phoronix has gotten sloppy with
using a common set of optimization flags in their gcc vs clang benchmarks.
Although, it is getting harder to make direct comparisons. Clang now
autovectorizes at -O2 while, as you can see from the my prior posting of
the assembly from-fverbose-asm -O2, FSF gcc 4.9.0 doesn't.
           Jack



On Wed, Jun 4, 2014 at 10:32 PM, Alexey Bataev <a.bataev at hotmail.com> wrote:

> Jack,
> Actually everything is quite simple. Config files for Phoronix test suites
> are using gcc by default and -O2 is provided by default in this config
> files. I think they just compiled these tests by gcc with the default
> config (which already includes -O2) while for clang they had to specify
> some custom options (like "-fopenmp -lgomp", though the second one is not
> needed), but forget to add any optimization options.
>
> Best regards,
> Alexey Bataev
> =============
>
> Software Engineer
> Intel Compiler Team
>
> 04.06.2014 22:19, openmp-dev-request at cs.uiuc.edu пишет:
>
>> Message: 4
>> Date: Wed, 4 Jun 2014 14:19:49 -0400
>> From: Jack Howarth<howarth.mailing.lists at gmail.com>
>> To: Andrey Bokhanko<andreybokhanko at gmail.com>
>> Cc:"openmp-dev at dcs-maillist2.engr.illinois.edu"
>>         <openmp-dev at dcs-maillist2.engr.illinois.edu>
>> Subject: Re: [Openmp-dev] Phoronix numbers for clang-omp compiler
>> Message-ID:
>>         <CADtEn-2YdnYNjg3bOcbGxJCJB87fdPyq1oAo
>> k4ZFoBTD33Y8Ag at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>>
>> Andrey,
>>       FSF gcc is not exactly defaulting to -O2 but certainly is higher
>> than
>> the default optimizations on clang?.
>>
>>
>> % touch t.cc
>> % g++-fsf-4.9 -fverbose-asm t.cc -S
>> % more t.s
>> # GNU C++ (GCC) version 4.9.0 (x86_64-apple-darwin11.4.2)
>> #       compiled by GNU C version 4.9.0, GMP version 6.0.0, MPFR version
>> 3.1.2, MPC version 1.0.2
>> # GGC heuristics: --param ggc-min-expand=100 --param
>> ggc-min-heapsize=131072
>> # options passed:  -D__DYNAMIC__ t.cc -fPIC -mmacosx-version-min=10.7.4
>> # -mtune=core2 -fverbose-asm
>> # options enabled:  -Wnonportable-cfstrings -fPIC
>> # -faggressive-loop-optimizations -fasynchronous-unwind-tables
>> # -fauto-inc-dec -fcommon -fdelete-null-pointer-checks -fearly-inlining
>> # -feliminate-unused-debug-types -fexceptions -ffunction-cse -fgcse-lm
>> # -fgnu-unique -fident -finline-atomics -fira-hoist-pressure
>> # -fira-share-save-slots -fira-share-spill-slots -fivopts
>> # -fkeep-static-consts -fleading-underscore -fmath-errno
>> # -fmerge-debug-strings -fnext-runtime -fobjc-abi-version= -fpeephole
>> # -fprefetch-loop-arrays -freg-struct-return
>> # -fsched-critical-path-heuristic -fsched-dep-count-heuristic
>> # -fsched-group-heuristic -fsched-interblock -fsched-last-insn-heuristic
>> # -fsched-rank-heuristic -fsched-spec -fsched-spec-insn-heuristic
>> # -fsched-stalled-insns-dep -fshow-column -fsigned-zeros
>> # -fsplit-ivs-in-unroller -fstrict-volatile-bitfields -fsync-libcalls
>> # -ftrapping-math -ftree-coalesce-vars -ftree-cselim -ftree-forwprop
>> # -ftree-loop-if-convert -ftree-loop-im -ftree-loop-ivcanon
>> # -ftree-loop-optimize -ftree-parallelize-loops= -ftree-phiprop
>> # -ftree-reassoc -ftree-scev-cprop -funit-at-a-time -funwind-tables
>> # -fverbose-asm -fzero-initialized-in-bss -gstrict-dwarf
>> # -m128bit-long-double -m64 -m80387 -malign-stringops -matt-stubs
>> # -mconstant-cfstrings -mfancy-math-387 -mfp-ret-in-387 -mfxsr -mieee-fp
>> # -mlong-double-80 -mmmx -mno-sse4 -mpush-args -mred-zone -msse -msse2
>> # -msse3
>>
>>          .constructor
>>          .destructor
>>          .align 1
>>          .subsections_via_symbols
>>
>> % g++-fsf-4.9 -fverbose-asm -O2 t.cc -S
>> % more t.s
>> # GNU C++ (GCC) version 4.9.0 (x86_64-apple-darwin11.4.2)
>> #       compiled by GNU C version 4.9.0, GMP version 6.0.0, MPFR version
>> 3.1.2, MPC version 1.0.2
>> # GGC heuristics: --param ggc-min-expand=100 --param
>> ggc-min-heapsize=131072
>> # options passed:  -D__DYNAMIC__ t.cc -fPIC -mmacosx-version-min=10.7.4
>> # -mtune=core2 -O2 -fverbose-asm
>> # options enabled:  -Wnonportable-cfstrings -fPIC
>> # -faggressive-loop-optimizations -fasynchronous-unwind-tables
>> # -fauto-inc-dec -fbranch-count-reg -fcaller-saves
>> # -fcombine-stack-adjustments -fcommon -fcompare-elim -fcprop-registers
>> # -fcrossjumping -fcse-follow-jumps -fdefer-pop
>> # -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively
>> # -fearly-inlining -feliminate-unused-debug-types -fexceptions
>> # -fexpensive-optimizations -fforward-propagate -ffunction-cse -fgcse
>> # -fgcse-lm -fgnu-unique -fguess-branch-probability -fhoist-adjacent-loads
>> # -fident -fif-conversion -fif-conversion2 -findirect-inlining -finline
>> # -finline-atomics -finline-functions-called-once -finline-small-functions
>> # -fipa-cp -fipa-profile -fipa-pure-const -fipa-reference -fipa-sra
>> # -fira-hoist-pressure -fira-share-save-slots -fira-share-spill-slots
>> # -fisolate-erroneous-paths-dereference -fivopts -fkeep-static-consts
>> # -fleading-underscore -fmath-errno -fmerge-constants
>> -fmerge-debug-strings
>> # -fmove-loop-invariants -fnext-runtime -fobjc-abi-version=
>> # -fomit-frame-pointer -foptimize-sibling-calls -foptimize-strlen
>> # -fpartial-inlining -fpeephole -fpeephole2 -fprefetch-loop-arrays -free
>> # -freg-struct-return -freorder-blocks -freorder-blocks-and-partition
>> # -freorder-functions -frerun-cse-after-loop
>> # -fsched-critical-path-heuristic -fsched-dep-count-heuristic
>> # -fsched-group-heuristic -fsched-interblock -fsched-last-insn-heuristic
>> # -fsched-rank-heuristic -fsched-spec -fsched-spec-insn-heuristic
>> # -fsched-stalled-insns-dep -fschedule-insns2 -fshow-column -fshrink-wrap
>> # -fsigned-zeros -fsplit-ivs-in-unroller -fsplit-wide-types
>> # -fstrict-aliasing -fstrict-overflow -fstrict-volatile-bitfields
>> # -fsync-libcalls -fthread-jumps -ftoplevel-reorder -ftrapping-math
>> # -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch
>> # -ftree-coalesce-vars -ftree-copy-prop -ftree-copyrename -ftree-cselim
>> # -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre
>> # -ftree-loop-if-convert -ftree-loop-im -ftree-loop-ivcanon
>> # -ftree-loop-optimize -ftree-parallelize-loops= -ftree-phiprop -ftree-pre
>> # -ftree-pta -ftree-reassoc -ftree-scev-cprop -ftree-sink -ftree-slsr
>> # -ftree-sra -ftree-switch-conversion -ftree-tail-merge -ftree-ter
>> # -ftree-vrp -funit-at-a-time -funwind-tables -fverbose-asm
>> # -fzero-initialized-in-bss -gstrict-dwarf -m128bit-long-double -m64
>> # -m80387 -malign-stringops -matt-stubs -mconstant-cfstrings
>> # -mfancy-math-387 -mfp-ret-in-387 -mfxsr -mieee-fp -mlong-double-80 -mmmx
>> # -mno-sse4 -mpush-args -mred-zone -msse -msse2 -msse3 -mvzeroupper
>>
>>          .constructor
>>          .destructor
>>          .align 1
>>          .subsections_via_symbols
>>
>> You might consider filing an enhancement request for clang 3.5 to have the
>> default behavior without optimization flags bumped up to -O1.
>>           Jack
>>
>
>
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